### Question summary
How can I vary the thickness of the edges/lines of polygons when they are symbolized using the "Bivariate Colors" option?

### Explanation, context and what I tried
When I symbolize a polygon layer using the "Graduated Colors" symbology option, I can edit the thickness of the polygon's edges/lines using the "Format all symbols" item inside the "More" drop down menu.

[![Graduated Colors][1]][1]

However, when I symbolize a polygon layer using the "Bivariate Colors" symbology option, I simply cannot find a way to edit the thickness of the polygons' lines/edges. 

[![Bivariate Colors][2]][2]

I've tried all of the sub-menus, but wasn't able to find out where this can be edited. I even tried a workaround of using the "Vary symbology by attribute" and setting a constant value, but that didn't work either:

[![Vary symbology by attribute][3]][3]

### Software version

I'm using ArcGIS Pro 2.9.3.


  [1]: https://i.sstatic.net/WrYlN.png
  [2]: https://i.sstatic.net/BG3vS.png
  [3]: https://i.sstatic.net/vx9qp.png